An electro-photographic type image forming apparatus such as a laser printer and an LED printer is known in the art. The image forming apparatus uses a developing cartridge.
Prior art discloses a conventional developing cartridge configured to be attached to a drum cartridge. The drum cartridge includes a lock lever. The developing cartridge includes a coupling and a lock rib configured to be engaged with the lock lever in a case where the developing cartridge is attached to the drum cartridge. With this configuration, the developing cartridge is locked relative to the drum cartridge at its attached position. A rotational driving force is applied to the coupling.